Combine ½ cup of your cold ice water and all of your gelatin in bowl of KitchenAid stand mixer affixed with whisk attachment.
In medium saucepan over medium-high heat, stir to combine the second half of ice cold water, sugar, corn syrup and salt.
Cover with lid and allow mixture to cook for 3 minutes.
Once the 3 minutes have passed, remove the lid, attach your candy thermometer, and continue to cook until temperature reaches 240 F (this may take 8-10 minutes. There is no need to stir while this is cooking).
As soon as thermometer indicates that temperature has reached 240F, remove mixture from heat.
Turn your KitchenAid (fitted with whisk attachment) on low speed and carefully pour hot mixture into the bowl with the gelatin.
Increase speed to high and whisk for 13-14 minutes (mixture will become very light and fluffy).
While your mixture is whisking, carefully grease the sides and bottom of a 13x9 pan with shortening. Additionally, lightly grease a rubber spatula that you will use to transfer the marshmallow mix to the pan.
In a medium-sized bowl, sift together powdered sugar and cornstarch. Liberally sprinkle this mixture over the shortening-prepared pan, shaking the contents to be sure to coat the bottom and sides completely with powder.
Save any excess powder by tapping it back into the medium-sized bowl that it was mixed in (you will need this later).
When marshmallow mix has been whisking for 14 minutes, reduce speed to low, add peppermint and vanilla extracts, return speed to high and beat one more minute.
Using your lightly greased spatula, evenly spread marshmallow mix into the bottom of your prepared 13x9 pan.
Drop several drops of red food coloring (I used a gel food coloring) over the surface of the marshmallows and then use a butter knife to swirl the color through the marshmallows as desired (try to not scrape the bottom of the pan with your knife--this may scrape away the shortening/powder mixture and your marshmallows may stick to the pan).
Lightly dust the top of the marshmallows with your reserved powdered sugar/cornstarch mixture. Do not discard this as you will use it again once you cut your marshmallows (if needed you can easily make more of this mixture by just using a 1:1 ratio of powdered sugar to cornstarch. Do NOT omit the cornstarch, otherwise you could have a very sticky mess on your hands).
Allow marshmallows to sit at least 4 hours before cutting (I prefer mine to sit overnight).
Once marshmallows have set, run a butter knife around the edge of the pan to gently loosen the marshmallows and invert the pan onto a cutting board (if the marshmallow doesn't want to budge, a rubber spatula can help persuade it to come loose).
Use a pizza cutter to cut the marshmallows into desired size/shape and dust the newly-cut edges with your powdered sugar/cornstarch mix.
Prepare your chocolate for dipping by melting white chocolate chips and shortening together in microwave at 15-second intervals (stirring well after each) until white chocolate is completely melted.
Prepare a cookie sheet with wax paper and set aside.
Gently brush as much excess powder from the bottoms of your marshmallows as is possible.
Dip the bottoms of your marshmallows into the melted white chocolate and then set on prepared cookie sheet until chocolate has hardened (about 10-20 minutes).
Peppermint Marshmallows https://sugarspunrun.com/homemade-peppermint-marshmallows/ Find more great recipes at SugarSpunRun.com!